Pointer position detection method

ABSTRACT

A pointer position detection method performed by a sensor controller connected to a sensor pattern includes: detecting a pen signal transmitted via a pen electrode provided at a distal end of an active pen, detecting a position of the active pen based on a level of the pen signal detected; detecting one or more candidate touch positions of a passive pointer that does not transmit a signal by detecting one or more changes of one or more capacitances of the sensor pattern, and outputting, as the position of the passive pointer, the one or more candidate touch positions remaining after excluding the position of the active pen from the one or more candidate touch positions.

BACKGROUND Technical Field

The present disclosure relates to a pointer position detection method,and more particularly to a pointer position detection method forperforming parallel detection of an active capacitance type electronicpen and a passive pointer such as a finger.

Background Art

An electronic pen of an electromagnetic resonance type (hereinafterreferred to as “EMR pen”) has been known. The EMR pen is an electronicpen configured to transmit an alternating magnetic field from a pen tip.A distal end of the EMR pen is constituted by a non-conductor such asresin so as not to disturb the alternating magnetic field.

Recently, development of an active capacitance type pen (hereinafterreferred to as “active pen”) has been in progress. The active pen is anelectronic pen configured to transmit signals from a pen tip byutilizing an electric field. A distal end of the active pen includes aconductor such as metal functioning as an antenna for generating anelectric field (i.e., pen electrode).

In addition, use of a finger, or an auxiliary device which does nottransmit signals similarly to a finger (hereinafter collectivelyreferred to as “passive pointer”), for example, together with anelectronic pen has been increasing in recent years. For example, afinger of a left hand or an auxiliary device is used to perform anauxiliary operation such as zoom-in, zoom-out, and rotation whiledrawing a picture using an electronic pen held by a right hand. In thiscase, a position detector for detecting a pointer needs to executeparallel detection of the electronic pen and the passive pointer.

Japanese Patent No. 4787087 (hereinafter, Patent Document 1) disclosesan example of a position detector which performs parallel detection ofan EMR pen and a passive pointer. As illustrated in FIG. 4 of thisliterature, the position detector executing parallel detection of theEMR pen and the passive pointer is required to prepare sensorsseparately used for the respective detections. The sensor for detectingthe EMR pen has a function of generating an alternating magnetic field,and a function of receiving a signal transmitted from the EMR pen. Onthe other hand, the sensor for detecting the passive pointer has afunction of detecting capacity coupling formed between a distal end ofthe passive pointer (e.g., finger tip) and an electrode disposed insidethe sensor. The passive pointer does not transmit a signal in responseto an alternating magnetic field, while the EMR pen does not formcapacity coupling with the electrode inside the sensor. Accordingly,detection of the EMR pen and detection of the passive pointer can beexecuted perfectly at the same timing (not in time-divided manner).

Furthermore, Japanese Patent No. 6,082,172 discloses an example of aposition detector which performs parallel detection of an active pen anda passive pointer. As illustrated in FIG. 6 of this literature,detection of the active pen and detection of the passive pointer areexecuted by using the same sensor. This sensor achieves detection of thepassive pointer by detecting capacity coupling formed between a distalend of the passive pointer and an electrode disposed inside the sensorsimilarly to the sensor for detecting the passive pointer described inPatent Document 1. However, this sensor achieves detection of the activepen by transmitting a signal to the active pen, and receiving a signaltransmitted from the active pen in response to the transmitted signal.In this case, each of a conductor disposed at the distal end of theactive pen (i.e., pen electrode) and the electrode disposed inside thesensor functions as an antenna for transmitting and receiving signals.In the configuration that detection of the passive pointer and detectionof the active pen are performed by the same sensor as in this example,detection of the active pen and detection of the passive pointer aredifficult to execute perfectly at the same timing, and therefore areexecuted in a time-divided manner.

A conventional position detector which executes parallel detection of anactive pen and a passive pointer produces a problem of mutualmisrecognition between a contact position of the active pen and acontact position of the passive pointer, wherefore improvement has beendemanded in this point. This problem is hereinafter detailed.

First, the position detector misrecognizes the contact position of theactive pen as the contact position of the passive pointer becausecapacity coupling is formed between the pen electrode of the active penand the electrode inside the sensor. The position detector does notdistinguish this capacity coupling from capacity coupling formed by thecontact of the passive pointer, and therefore misrecognizes the contactof the active pen as the contact of the passive pointer. Recently, thenumber of a position detector configured to distinguish between aplurality of passive pointers is increasing. However, this type ofposition detector misrecognizes contact of the active pen as contact ofthe second or third passive pointer.

Second, the position detector misrecognizes the contact position of thepassive pointer as the contact position of the active pen because atransmission signal of the active pen is conducted to a palm or the likevia a human body, and then transmitted to the sensor from the palm orthe like. The position detector does not distinguish between the signalthus received and a signal directly transmitted from the pen electrodeof the active pen, and therefore misrecognizes the contact position ofthe palm as the contact position of the active pen.

BRIEF SUMMARY

Accordingly, an object of the present disclosure is to provide a pointerposition detection method capable of achieving correct distinctionbetween a contact position of an active pen and a contact position of apassive pointer.

In addition, detection of an active pen and detection of a passivepointer are executed in a time-divided manner as described above.Assuming that a time required for detection of the active pen is set to3 milliseconds for each detection, that a time required for detection ofthe passive pointer is set to 2 milliseconds for each detection, andthat detection of the active pen and detection of the passive pointerare alternately executed, a detection rate of the active pen and adetection rate of the passive pointer are equalized (about 200 (⅕×1,000)detections per second for both).

In this case, such a method which detects the passive pointer oncesubsequently to successive detection of the active pen twice isconsidered, for example, for further improvement of the detection rateof the active pen.

However, when a control method which simply executes detection of theactive pen and detection of the passive pen at any appropriate ratio ofthe respective detections as described above, intervals of detection ofthe active pen may become irregular. According to the example describedabove, for example, after successive execution of detection of theactive pen twice, subsequent detection of the active pen is notperformed until completion of detection of the passive pointer. In thiscase, an unnatural drawing result may be produced in such a drawingapplication which operates based on an expectation that coordinate dataindicating the active pen and sequentially output from a sensorcontroller is transmitted at regular intervals in view of time, forexample. Accordingly, improvement has been demanded in this point.

Another object of the present disclosure therefore is to provide apointer position detection method capable of executing detection of anactive pen at regular intervals while maintaining detection rates ofboth the active pen and a passive pointer.

A position detector detecting an active pen may misrecognize a positionnot in contact with the active pen and a passive pointer as a contactposition of the active pen. This misrecognition is caused when such acurrent path is formed which extends from a pen electrode of the activepen, passes through an electrode inside a sensor, enters an arm oppositeto a hand holding the active pen, passes through a human body, andreturns to the active pen. In this case, a transmission signal of theactive pen may be detected below the corresponding arm. The contactposition of the active pen misrecognized in this manner is hereinafterreferred to as a “ghost position.”

For example, when the active pen suddenly shifts to the inside of atouch surface from a bezel region of a tablet constituting the positiondetector, the position detector may detect a ghost position beforedetection of an actual pen position. In this case, an unnecessary linesegment is drawn between the detected ghost position and the actual penposition detected immediately after the detection of the ghost position.Accordingly, improvement has been demanded in this point.

A further object of the present disclosure therefore is to provide apointer position detection method capable of preventing drawing of anunnecessary line segment caused by presence of a ghost position.

An aspect of the present disclosure is directed to a pointer positiondetection method performed by a sensor controller connected to a sensorpattern. The method includes: detecting a pen signal transmitted via apen electrode provided at a distal end of an active pen, detecting aposition of the active pen based on a level of the pen signal detected,detecting one or more candidate touch positions of the passive pointerby detecting one or more changes of one or more capacitances of thesensor pattern, and outputting, as a position of the passive pointer,the one or more candidate touch positions remaining after excluding theposition of the active pen from the one or more candidate touchpositions.

Another aspect of the present disclosure is directed to a pointerposition detection method for detecting a position of a pointer presentwithin a predetermined region. The method includes: performing 1/N of afirst detection process at a first detection rate, including acquiringpartial detection data that indicates whether a first pointer isdetected based on the performing of the 1/N of the first detectionprocess, and storing the partial detection data in a memory; combining(N−1) partial detection data already stored in the memory and thepartial detection data responsive to the partial detection data beingstored in the memory by the storing, including generating detection datathat indicates whether the first pointer is detected throughout thepredetermined region; and outputting the detection data at the firstdetection rate.

A further aspect of the present disclosure is directed to a pointerposition detection method for detecting a position of a pointer presentwithin a predetermined region. The method includes: performing 1/N of afirst detection process at a first detection rate, including acquiringpartial detection data that indicates whether a first pointer is presentwithin the predetermined region, and storing the partial detection datain a memory; and performing a second process at a second detection rateto detect a second pointer, the second pointer being different from thefirst pointer. The second detection process and the first detectionprocess are alternately performed.

A still further aspect of the present disclosure is directed to apointer position detection method for detecting a pointer present withina predetermined region including K first electrodes and K secondelectrodes. The method includes: sequentially reading from a memory onepulse group among N×M pulse groups each including K pulses, includingtransmitting the K pulses included in the one pulse group to each of theK first electrodes every time the one pulse group is read by thereading, and storing in the memory partial detection data that indicateslevels of signals output from each of the K second electrodes as aresult of the transmitting; and combining the partial detection datacorresponding to respective M pulse groups and stored by the storingwith the partial detection data already stored in the memory andcorresponding to (N−1)×M pulse groups for each of the second electrodesevery time the partial detection data is stored in the memory by thestoring, and generating combined detection data that indicates whetherthe pointer is present on a corresponding second electrode.

A still further aspect of the present disclosure is directed to apointer position detection method performed by a sensor controller. Themethod includes: detecting a position of a passive pointer that does nottransmit a signal by detecting a change of a capacitance in the sensorpattern, and determining a palm region; detecting a pen signaltransmitted via s pen electrode provided at a distal end of an activepen, and detecting a position of the active pen based on a level of thepen signal detected; and outputting pen-up information indicating thatthe active pen is separated from a touch surface (1) in response todetermining that a previously detected position of the active pen lieswithin a predetermined region formed based on the palm region, and (2)in response to determining that a distance between a currently detectedposition of the active pen and the previously detected position of theactive pen exceeds a predetermined value.

A still further aspect of the present disclosure is directed to apointer position detection method executed by a sensor controller. Themethod includes: detecting a position of a passive pointer that does nottransmit a signal by detecting a change of a capacitance in the sensorpattern, and determining a palm region; and detecting a pen signaltransmitted via a pen electrode provided at a distal end of an activepen, detecting a position of the active pen based on a level of the pensignal detected, detecting a writing pressure based on the pen signaltransmitted from the active pen, and determining whether the position ofthe active pen is located proximate to the palm region. When theposition of the active pen is determined to be proximate to the palmregion, the pen position is invalidated in a case where the writingpressure is determined to be invalid, and the position of the active penis validated in a case where the writing pressure is determined to bevalid.

The pointer position detection method according to the presentdisclosure is capable of selecting one or more candidate touch positionsoutput as a passive pointer position in accordance with an active penposition retained in a memory. Accordingly, correct distinction betweena contact position of an active pen and a contact position of a passivepointer is achievable.

The pointer position detection method according to the presentdisclosure divides a first detection process (passive pointer positiondetection process) into N processes, and executes the divided processes.Accordingly, the method can detect the active pen at regular intervalswhile maintaining detection rates of both the active pen and the passivepointer.

The pointer position detection method according to the presentdisclosure is capable of outputting pen-up information when a distancebetween a pen positon currently detected and a pen position previouslydetected exceeds a predetermined value. Accordingly, drawing of anunnecessary line segment caused by presence of a ghost position isavoidable.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a view illustrating an example of a state of use of a positiondetection system according to a first embodiment of the presentdisclosure;

FIG. 2 is a flowchart depicting an outline of a pointer positiondetection process executed by a sensor controller included in a positiondetector according to a related art of the present disclosure;

FIG. 3 is a flowchart depicting an outline of a pointer positiondetection process executed by a sensor controller according to anembodiment of the present disclosure;

FIG. 4 is a diagram depicting a configuration of a tablet illustrated inFIG. 1;

FIG. 5 is a diagram depicting a principle of a position detectionprocess executed by an MCU depicted in FIG. 4 to detect a position of afinger;

FIG. 6A depicts a pen position table used in an output positiondetermination process according to an embodiment of the presentdisclosure, while FIG. 6B depicts a touch position table used in theoutput position determination process according to an embodiment of thepresent disclosure;

FIG. 7 is a diagram depicting an example of the output positiondetermination process performed by the MCU with reference to the penposition table and the touch position table depicted in FIGS. 6A and 6B;

FIG. 8 is a diagram depicting an example of the output positiondetermination process performed by the MCU with reference to the penposition table and the touch position table depicted in FIGS. 6A and 6B;

FIG. 9 is a flowchart depicting details of the flowchart depicted inFIG. 3;

FIG. 10 is a flowchart depicting details of the flowchart depicted inFIG. 3;

FIG. 11 is a flowchart depicting a pointer position detection processexecuted by the sensor controller according to a fourth modified exampleof an embodiment of the present disclosure;

FIG. 12A is a chart depicting a control sequence of the pointer positiondetection process according to the related art of the presentdisclosure, while FIG. 12B is a chart depicting a control sequence ofthe pointer position detection process according to an embodiment of thepresent disclosure;

FIG. 13 is a diagram depicting an example of a finger detection signalFDS used together with a 16×16 sensor;

FIGS. 14A and 14B are diagrams depicting a first example of contents ofa 1/N process according to ab embodiment of the present disclosure;

FIGS. 15A and 15B are diagrams depicting a second example of thecontents of the 1/N process according to an embodiment of the presentdisclosure;

FIGS. 16A and 16B are diagrams depicting a third example of the contentsof the 1/N process according to an embodiment of the present disclosure;

FIGS. 17A and 17B are diagrams depicting a fourth example of thecontents of the 1/N process according to an embodiment of the presentdisclosure;

FIGS. 18A and 18B are diagrams depicting a fifth example of the contentsof the 1/N process according to an embodiment of the present disclosure;

FIG. 19 is a diagram depicting an example of specific storage contentsof a shift register according to the fifth example;

FIG. 20 is a diagram depicting another example of the specific storagecontents of the shift register according to the fifth example;

FIG. 21A is a chart depicting a control sequence of a pointer positiondetection process according to a first modified example of an embodimentof the present disclosure,

FIG. 21B is a chart depicting a control sequence of a pointer positiondetection process according to a second modified example of anembodiment of the present disclosure, and FIG. 21C is a chart depictinga control sequence of a pointer position detection process according toa third modified example of an embodiment of the present disclosure;

FIG. 22 is a view illustrating an example of a state of use of theposition detection system according to a second embodiment of thepresent disclosure;

FIG. 23 is a diagram depicting an operation of a host processoraccording to a related art of the second embodiment of the presentdisclosure; and

FIG. 24 is a flowchart depicting an outline of a pointer positiondetection process executed by the sensor controller according to thesecond embodiment of the present disclosure.

DETAILED DESCRIPTION

Embodiments according to the present disclosure are hereinafterdescribed in detail with reference to the accompanying drawings.

FIG. 1 is a view illustrating an example of a state of use of a positiondetection system 1 according to a first embodiment of the presentdisclosure. As illustrated in this figure, the position detection system1 according to the present embodiment includes an active pen 2 and atablet 3. The tablet 3 has a touch surface 3 a, and is configured todetect positions of the active pen and a passive pointer on the touchsurface 3 a. FIG. 1 illustrates a state in which a pen tip of the activepen 2, a distal end of a finger 4 as a passive pointer, and a hand 5 ofa user holding the active pen 2 are in contact with the touch surface 3a. The finger 4 of the user is presented as an example of the passivepointer. The type of the passive pointer according to the presentembodiment is not particularly limited. In the following description,the active pen 2, and the passive pointer such as the finger 4 as atypical example are also collectively referred to as “pointers.”

Before describing details of the present embodiment, an outline of thepresent disclosure is touched upon herein with reference to FIGS. 2 and3.

Initially, FIG. 2 is a flowchart depicting an outline of a pointerposition detection process executed by a sensor controller (notdepicted) included in a tablet according to a related art of the presentdisclosure. As depicted in this figure, the sensor controller accordingto the related art of the present disclosure is configured to repeatedlyexecute processing at S101 to S106 (S100).

The processing at S101 to S106 is specifically described. The sensorcontroller initially executes a position detection process for theactive pen 2 (S101), and outputs a detected position to a host processor(not depicted) (S102). Subsequently, the sensor controller againexecutes the position detection process for the active pen 2 (S103), andoutputs a detected position to the host processor (S104). The sensorcontroller then executes a position detection process for the finger 4(S105), and outputs a detected position to the host processor (S106).

As described above, the position detection process for the active pen 2is successively performed twice at S101 and S103 to obtain a sufficientdetection rate for the active pen 2. In this case, however, detectionintervals for the active pen 2 become irregular, in which condition, asdescribed above, an unnatural drawing result may be produced in adrawing application operating based on an expectation that coordinatedata indicating the active pen 2 and sequentially output from the sensorcontroller is transmitted at regular intervals in view of time, forexample.

Moreover, as described above, a contact position of the hand 5 may bemisdetected as a position of the active pen during the positiondetection process for the active pen 2. On the other hand, the contactposition of the active pen 2 or the hand 5 may be detected as theposition of the finger 4 during the position detection process for thefinger 4.

A process performed by a sensor controller 31 (see FIG. 4 referred tobelow) included in the tablet 3 according to the present embodiment isconfigured to overcome these problems. An outline of this process ishereinafter described with reference to FIG. 3.

FIG. 3 is a flowchart depicting an outline of a pointer positiondetection process executed by the sensor controller 31. As illustratedin this figure, the sensor controller 31 is configured to repeatedlyexecute processing at S2 to S9 (S1). S2 to S4 are associated with a pendetection process for detecting a pen position corresponding to theposition of the active pen 2, while S5 to S9 are associated with a touchdetection process for detecting a passive pointer position correspondingto the position of the finger 4.

The processing at S2 to S9 is now specifically described in comparisonwith the process depicted in FIG. 2. Initially, the position detectionprocess at S2 is similar to the position detection process at S101.However, an output process for outputting a detected position isdifferent from the corresponding process at S102 of the related art.More specifically, rather than outputting the position detected at S2 toa host processor 32 (see FIG. 4 referred to below) without change, thesensor controller 31 is configured to perform a process for selectingand determining a pen position from one or more detected positions(candidate pen positions) (hereinafter referred to as “pen positiondetermination process”) (S3), and outputting only the determined penposition to the host processor 32 (S4). Specific contents of the penposition determining process will be described below. The contactposition of the hand 5 is excluded from output targets during thisprocess, wherefore the sensor controller 31 can correctly identify thecontact position of the active pen 2.

Subsequently, the sensor controller 31 performs a position detectionprocess for the finger 4 at S5. In this case, the sensor controller 31performs only 1/N of the position detection process executed at S105 byone process (S5). Specific contents of the 1/N process will be describedbelow. At S5, only the 1/N process is executed by one process, whereforethe sensor controller 31 needs to combine N results to obtain theposition of the finger 4. Accordingly, the sensor controller 31 recordsdata indicating a partial detection result obtained by the 1/N process(hereinafter referred to as “partial detection data”) (S6), and combinesthe partial detection data with (N−1) partial detection data previouslyrecorded to generate data indicating the position of the finger 4(hereinafter referred to as “entire detection data”) (S7). In this case,the 1/N process is completed substantially in 1/N of the time requiredfor completing the position detection process executed at S105,wherefore a sufficient detection rate of the active pen 2 can beobtained by the process configured as at S5 to S7 and performed by thesensor controller 31 without a necessity of successive execution of theposition detection process for the active pen 2 twice as in the exampleof FIG. 2.

Thereafter, the sensor controller 31 performs a process for selectingand determining a passive pointer position from one or more positionsindicated by the entire detection data generated at S7 (candidate touchpositions) (hereinafter referred to as “passive pointer positiondetermination process”) (S8), and outputs only the determined passivepointer position to the host processor 32 (S9). The purpose forexecuting processing at S8 and S9 is similar to the purpose of S3 andS4. By this processing, the contact positions of the active pen 2 andthe hand 5 are excluded from output targets, wherefore the sensorcontroller 31 can correctly identify the contact position of the finger4. Specific contents of the passive pointer position determinationprocess will be also described below. The pen position determinationprocess and the passive pointer position determination process are alsohereinafter collectively referred to as an “output positiondetermination process.”

Description of the outline of the present disclosure is now completed.The details of the present embodiment are hereinafter described againwith reference to FIG. 1. In the following description, a generalconcept of a configuration of the position detection system 1 accordingto the present embodiment is initially described, and then details ofthe output position determination process and the 1/N process describedabove are sequentially described.

The active pen 2 is an electronic pen which operates by an activecapacitance system. Not-depicted control circuitry and transmission andreception circuitry are provided inside the active pen 2. The controlcircuitry is configured to transmit and receive signals to and from thetablet 3 via the transmission and reception circuitry. A signaltransmitted from the tablet 3 to the active pen 2 is hereinafterreferred to as an uplink signal US, while a signal transmitted from theactive pen 2 to the tablet 3 (pen signal) is hereinafter referred to asa downlink signal DS.

A pen electrode is provided at the distal end of the active pen 2. Thetransmission and reception section of the active pen 2 receives theuplink signal US and transmits the downlink signal DS via a capacitanceformed between the pen electrode and a sensor 30 (see FIG. 4 referred tobelow) provided on the touch surface 3 a of the tablet 3. The penelectrode for receiving the uplink signal US and the pen electrode fortransmitting the downlink signal DS may be constituted by differentelectrodes, or the same electrode.

The active pen 2 also includes writing pressure detection circuitry fordetecting a pressure (writing pressure) applied to the pen tip, sideswitch state detection circuitry for detecting on-off state of a sideswitch provided on the side surface, a storage device (memory) forstoring unique identifiers (IDs) allocated beforehand, and a powersource device (battery) for supplying operation power of the active pen2. The control circuitry of the active pen 2 is configured to controlthese components.

The downlink signal DS includes a position signal which is a burstsignal at a predetermined frequency, and a data signal containing datato be transmitted from the active pen 2 to the tablet 3. The positionsignal is used to detect the position of the active pen 2 by the tablet3. For example, data transmitted via the data signal includes dataindicating a writing pressure detected by the writing pressure detectioncircuitry (writing pressure data), data indicating on-off state of theside switch and acquired by the side switch state detection circuitry(switch data), and unique IDs stored in the storage device, and isinserted into the data signal by the control circuitry.

The uplink signal US includes a predetermined start bit, and a commandindicating an instruction issued from the tablet 3 to the active pen 2.The control circuitry of the active pen 2 is configured to extract thecommand from the received uplink signal US, decode the extractedcommand, and insert data corresponding to contents of the command intothe data signal. In this manner, the tablet 3 is allowed to extractdesired data from the active pen 2.

The tablet 3 is an electronic device which has both a function as aliquid crystal display device, and a function as a position detector fordetecting a position of a pointer on the touch surface 3 a. The touchsurface 3 a is provided on a liquid crystal display screen. Examples ofthe pointer detectable by the tablet 3 include both the active pen 2 andthe finger 4 depicted in FIG. 1.

The sensor 30 including a plurality of sensor electrodes 30X and 30Y(sensor pattern) is provided inside the touch surface 3 a, as will bedescribed below in detail with reference to FIG. 4. The tablet 3 isconfigured to detect the position of the finger 4 (passive pointerposition) by detecting a change of a capacitance included in the sensor30, and detect the position of the active pen 2 (pen position) bydetecting the foregoing position signal using the sensor 30.

The respective sensor electrodes 30X also function as common electrodesof the liquid crystal display device. During a pixel driving operation,a pixel driving voltage Vcom, which is a fixed potential, to therespective sensor electrodes 30X. The tablet 3 of a type which includesposition detection sensor electrodes also functioning as liquid crystaldisplay electrodes as in this example is generally called an “in-celltype.” In case of the “in-cell type” tablet 3, the sensor electrodes 30Xduring pixel driving operation are difficult to use for positiondetection, wherefore position detection of the finger 4 or the activepen 2 is executed at an interval between pixel driving operations (e.g.,horizontal blanking period and vertical blanking period). However, thepresent disclosure is similarly applicable to a tablet of a type(non-in-cell type) which includes the plurality of sensors 30X and 30Yseparated from electrodes (common electrode and pixel electrode) of aliquid crystal display device.

FIG. 4 is a diagram depicting a configuration of the tablet 3. Asdepicted in this figure, the tablet 3 includes the sensor 30, the sensorcontroller 31, and the host processor 32.

The sensor 30 includes the plurality of sensor electrodes 30X and theplurality of sensor electrodes 30Y disposed in a matrix. The sensorelectrodes 30X each extend in a Y direction and are disposed at regularintervals in an X direction crossing the Y direction at right angles,while the sensor electrodes 30Y each extend in the X direction and aredisposed at regular intervals in the Y direction. According to theexample presented herein, both the sensor electrodes 30X and 30Y areeach constituted by a linear conductor. However, the sensor electrodes30X and 30Y may be each constituted by a conductor having a differentshape. For example, either the sensor electrodes 30X or the sensorelectrodes 30Y may be constituted by a plurality of rectangularconductors two-dimensionally disposed to detect two-dimensionalcoordinates of the active pen 2.

The sensor controller 31 is configured to communicate with the activepen 2 (including position detection of active pen 2), and detect theposition of the finger 4 in a time-divided manner by using the sensor 30at intervals between pixel driving operations. The sensor controller 31is further configured to supply the pixel driving voltage Vcom to eachof the plurality of sensor electrodes 30X during pixel drivingoperation. The configuration of the sensor controller 31 is hereinafterdescribed in more detail.

As depicted in FIG. 4, the sensor controller 31 includes a micro controlunit (MCU) 40, a logic circuit 41, transmission circuits 42 and 43, areception circuit 44, and a selection circuit 45.

The MCU 40 and the logic circuit 41 are control circuits for controllingtransmission and reception operations of the sensor controller 31 bycontrolling the transmission circuits 42 and 43, the reception circuit44, and the selection circuit 45. More specifically, the MCU 40 is amicroprocessor which contains a memory (read-only memory (ROM) andrandom-access memory (RAM)) inside, and executes programs stored in thememory to perform operations. Operation timing of the MCU 40 iscontrolled according to a timing signal supplied from the host processor32. Examples of operations performed by the MCU 40 include control anoperation for the logic circuit 41, an operation for supplying the pixeldriving voltage Vcom to the selection circuit 45, an operation forcausing the transmission circuit 42 to output a finger detection signalFDS, an operation for supplying, to the transmission circuit 43, acommand COM indicating contents of an instruction issued to the activepen 2, operation for detecting respective positions of the active pen 2and the finger 4 (more specifically, coordinates x, y indicatingpositions within touch surface 3 a) based on a digital signal suppliedfrom the reception circuit 44, operation for decoding the digital signalsupplied from the reception circuit 44 to acquire data Res (e.g.,writing pressure data, switch data, and unique ID described above)transmitted from the active pen 2, and operation for determining acontact state of the active pen 2 in contact with the touch surface 3 abased on writing pressure data contained in the data Res. The logiccircuit 41 has a function of outputting control signals ctrl_t1 toctrl_t4, and ctrl_r under control by the MCU 40.

The transmission circuit 42 is a circuit which generates the fingerdetection signal FDS under the control by the MCU 40, and supplies thefinger detection signal FDS to the respective sensor electrodes 30X viathe selection circuit 45. Specific contents of the finger detectionsignal FDS, and a method for supplying the finger detection signal FDSto the respective sensor electrodes 30X are herein described withreference to FIG. 5.

FIG. 5 is a diagram depicting the principle of the position detectionprocess executed by the MCU 40 to detect the position of the finger 4.This figure depicts a state before division of the position detectionprocess for the finger 4 into the 1/N process depicted in FIG. 3, i.e.,the position detection process for the finger 4 executed at S105depicted in FIG. 2. This figure depicts only the four sensor electrodes30X for simplifying the explanation, but there are actually provided alarger number of the sensor electrodes 30X. The description hereinaftercontinues on the assumption that the K sensor electrodes 30X areprovided.

As depicted in FIG. 5, the finger detection signal FDS is constituted byK signals S₁ to S_(k) which are K pulses each expressed as “1” or “−1,”for example. The respective nth pulses (n=1 to K) of the signals S₁ toS_(k) constitute a pulse group P_(n). The respective pulses constitutingthe one pulse group P_(n) are input from the transmission circuit 42depicted in FIG. 4 to the respective sensor electrodes 30X in parallelvia the selection circuit 45.

Now returning to FIG. 4, the transmission circuit 43 is a circuit whichgenerates the uplink signal US under the control by the MCU 40 and thelogic circuit 41, and supplies the uplink signal US to the selectioncircuit 45. As depicted in this figure, the transmission circuit 43includes a pattern supply circuit 50, a switch 51, a code stringretention circuit 52, a diffusion processing circuit 53, and atransmission guard circuit 54. It is assumed in the description hereinthat particularly the pattern supply circuit 50 among these componentsis included in the transmission circuit 43 according to the presentembodiment. However, the pattern supply circuit 50 may be included inthe MCU 40.

The pattern supply circuit 50 retains a start bit SB disposed at thehead of the uplink signal US, and is configured to output the retainedstart bit SB in accordance with an instruction of the control signalctrl_t1 supplied from the logic circuit 41,

The switch 51 has a function of selecting either the pattern supplycircuit 50 or the MCU 40 based on the control signal ctrl_t2 suppliedfrom the logic circuit 41, and supplying output of the selected one tothe diffusion processing circuit 53. When the switch 51 selects thepattern supply circuit 50, the start bit SB is supplied to the diffusionprocessing circuit 53. When the switch 51 selects the MCU 40, thecommand COM is supplied to the diffusion processing circuit 53.

The code string retention circuit 52 has a function of generating andretaining a diffusion code having a predetermined chip length andautocorrelation characteristics in response to the control signalctrl_t3 supplied from the logic circuit 41. The diffusion code retainedby the code string retention circuit 52 is supplied to the diffusionprocessing circuit 53.

The diffusion processing circuit 53 has a function of acquiring atransmission chip string having a predetermined chip length bymodulating the diffusion code, which is retained by the code stringretention circuit 52, based on a value supplied via the switch 51 (startbit SB or command COM). The diffusion processing circuit 53 supplies theacquired transmission chip string to the selection circuit 45 via thetransmission guard circuit 54.

The transmission guard circuit 54 has a function of inserting a guardperiod necessary for switching between the transmission operation andthe reception operation (period when both transmission and reception arenot performed) between the transmission period of the uplink signal USand the reception period of the downlink signal DS in response to thecontrol signal ctrl_t4 supplied from the logic circuit 41.

The selection circuit 45 includes switches 58 x and 58 y, and conductorselection circuits 59 x and 59 y.

The switch 58 y is a switch element configured to connect a commonterminal and either a T terminal or an R terminal. The common terminalof the switch 58 y is connected to the conductor selection circuit 59 y.The T terminal is connected to an output end of the transmission circuit43. The R terminal is connected to an input end of the reception circuit44. The switch 58 x is a switch element configured to connect a commonterminal and one of a T1 terminal, a T2 terminal, a D terminal, and an Rterminal. In an actual configuration, the T2 terminal among theseterminals is constituted by a collection of the same number of terminalsas the number of the sensor electrodes 30X. The common terminal of theswitch 58 x is connected to the conductor selection circuit 59 x. The T1terminal is connected to the output end of the transmission circuit 43.The T2 terminal is connected to an output end of the transmissioncircuit 42. The D terminal is connected to an output end of the MCU 40which outputs the pixel driving voltage Vcom. The R terminal isconnected to the input end of the reception circuit 44.

The conductor selection circuit 59 x is a switch element for selectivelyconnecting the plurality of sensor electrodes 30X to the common terminalof the switch 58 x. The conductor selection circuit 59 x is configuredto allow simultaneous connection between a part or all of the pluralityof sensor electrodes 30X and the common terminal of the switch 58 x. Ina state of connection between the T2 terminal and the common terminalwithin the switch 58 x, the conductor selection circuit 59 x connectsthe plurality of terminals constituting the T2 terminal and theplurality of sensor electrodes 30X with one-to-one correspondence.

The conductor selection circuit 59 y is a switch element for selectivelyconnecting the plurality of sensor electrodes 30Y to the common terminalof the switch 58 y. Similarly to the conductor selection circuit 59 x,the conductor selection circuit 59 y is configured to allow simultaneousconnection between a part or all of the plurality of sensor electrodes30Y and the common terminal of the switch 58 y.

Four control signals sTRX, sTRy, selX, and selY are supplied from thelogic circuit 41 to the selection circuit 45. More specifically, thecontrol signal sTRx is supplied to the switch 58 x. The control signalsTRy is supplied to the switch 58 y. The control signal selX is suppliedto the conductor selection circuit 59 x. The control signal selY issupplied to the conductor selection circuit 59 y. The logic circuit 41achieves transmission of the uplink signal US or the finger detectionsignal FDS, application of the pixel driving voltage Vcom, and receptionof the downlink signal SD or the finger detection signal FDS bycontrolling the selection circuit 45 using the control signals sTRx,sTRy, selX, and selY.

More specifically, at the time of transmission of the uplink signal US,the logic circuit 41 controls the selection circuit 45 to simultaneouslyconnect all of the plurality of sensor electrodes 30Y to thetransmission circuit 43. In this case, the uplink signal US issimultaneously transmitted from all of the plurality of sensorelectrodes 30Y. Accordingly, the active pen 2 located at any position onthe touch surface 3 a is capable of receiving the uplink signal US.

At the time of reception of the foregoing position signal included inthe downlink signal DS, the logic circuit 41 sequentially selects theplurality of sensor electrodes 30X and 30Y one by one, and controls theselection circuit 45 to connect the selected sensor electrodes 30X and30Y to the reception circuit 44. In this manner, the same number ofposition signals as the number of the sensor electrodes 30X and 30Y aresequentially supplied to the reception circuit 44. The MCU 40 isconfigured to detect the position of the active pen 2 based on levels ofthe position signals supplied to the reception circuit 44 in thismanner. This configuration will be described below in detail.

More specifically, the MCU 40 determines a level of a position signal ateach of intersections of the plurality of sensor electrodes 30X and 30Ybased on a digital signal (described below) supplied from the receptioncircuit 44. Then, the MCU 40 detects the position of the active pen 2based on respective levels thus determined. More specifically, a regionincluded in the touch surface 3 a and exhibiting higher levels of theposition signals than a predetermined value, and detects a centerposition, for example, of the region as the position of the active pen2.

At the time of reception of the foregoing data signal included in thedownlink signal DS, the MCU 40 initially selects one or more of theplurality of sensor electrodes 30X and 30Y. This selection is executedbased on the position of the active pen 2 detected from the positionsignal received immediately before. Thereafter, the logic circuit 41controls the selection circuit 45 to connect the selected sensorelectrodes 30X and 30Y to the reception circuit 44. In this manner, thedata signal transmitted from the active pen 2 can be supplied to thereception circuit 44.

At the time of transmission of the finger detection signal FDS, thelogic circuit 41 repeatedly performs, for the sensor electrodes 30Y, anoperation for selecting the one sensor electrode 30Y, and causing thetransmission circuit 42 to sequentially input the foregoing pulse groupsp₁ to p_(k) to the respective sensor electrodes 30X in cooperation withthe MCU 40. More specifically, the logic circuit 41 initially controlsthe selection circuit 45 to connect the plurality of terminalsconstituting the T2 terminal of the switch 58 x to the plurality ofsensor electrodes 30X with one-to-one correspondence. Thereafter, thelogic circuit 41 sequentially selects the plurality of sensor electrodes30Y one by one while maintaining this state, and controls the selectioncircuit 45 to connect the selected sensor electrode 30Y to the receptioncircuit 44.

The MCU 40 also sequentially reads the pulse groups p₁ to p_(k) from thememory one pulse group each during selection of the one sensor electrode30Y, and supplies K pulses constituting the read pulse group to thetransmission circuit 42 for each of the reading. The transmissioncircuit 42 inputs the K pulses thus supplied to the K sensor electrodes30X in parallel. A level of a digital signal supplied from the receptioncircuit 44 as a result of this control is a level reflecting changes ofcapacitances formed at respective intersections of the selected sensorelectrode 30Y and the respective sensor electrodes 30X. The MCU 40 istherefore configured to detect the position of the finger 4 based on thelevels of the digital signals supplied from the reception circuit 44.

The position detection process executed by the MCU 40 to detect theposition of the finger 4 is herein described in more detail again withreference to FIG. 5. The following description is presented on theassumption that the number of the sensor electrodes 30X is four (i.e.,K=4). However, the same description is applicable even when the numberof the sensor electrodes 30X is three or smaller or five or larger.

When the number of the sensor electrodes 30X is four, each of signals s₁to s_(k) is constituted by a pulse expressed by four numerals of “1” or“−1.” More specifically, as depicted in FIG. 5, the signal s₁ isconstituted by “1, 1, 1, 1,” the signal Ω is constituted by “1, 1, −1,−1,” the signal s₃ is constituted by “1, −1, −1, 1,” and the signal s₄is constituted by “1, −1, 1, −1.”

The MCU 40 functionally includes a shift register 40 a and a correlator40 b. The shift register 40 a is a first in first out (FIFO) typestorage unit, and is configured to store the same number (i.e., K) ofdata as the number of the sensor electrodes 30X. When storing new datain the shift register 40 a, data stored K times before is deleted. Asdescribed above, the MCU 40 and the logic circuit 41 repeated performsthe operation for the respective sensor electrodes 30Y, i.e., theoperation for selecting the one sensor electrode 30Y, and causing thetransmission circuit 42 to sequentially input the pulse groups p₁ to p₄to the respective sensor electrodes 30X. As a result, four levels L₁ toL₄ corresponding to the respective pulse groups p₁ to p₄ sequentiallyappear in the selected sensor electrode 30Y. The MCU 40 sequentiallyacquires the levels L₁ to L₄ appearing in the sensor electrodes 30Y inthis manner via the reception circuit 44, and stores the acquired levelsin the shift register 40 a every time the levels are acquired.

Specific contents of the levels L₁ to L₄ at the time of selection of thesensor electrode 30Y₁ depicted in FIG. 5 are now detailed by way ofexample. In the following description, it is assumed that capacitancesC₁₁ to C₄₁ are formed between the sensor electrode 30Y₁ and the foursensor electrodes 30X₁ to 30X₄, respectively.

Initially, the level L₁ corresponding to the pulse group p₁ and storedin the register 40 a is an inner product of a vector (C₁₁, C₂₁, C₃₁,C₄₁) and a vector (1, 1, 1, 1) indicating the pulse group p₁. This innerproduct is calculated as C₁₁+C₂₁+C₃₁+C₄₁ as depicted in FIG. 5.Similarly, the level L₂ corresponding to the pulse group p₂ and storedin the register 40 a is an inner product of the vector (C₁₁, C₂₁, C₃₁,C₄₁) and a vector (1, 1, −1, −1) indicating the pulse group p₂, and iscalculated as C₁₁+C₂₁−C₃₁−C₄₁. The level L₃ corresponding to the pulsegroup p₃ and stored in the register 40 a is an inner product of thevector (C₁₁, C₂₁, C₃₁, C₄₁) and a vector (1, −1, −1, 1) indicating thepulse group p₃, and is calculated as C₁₁−C₂₁−C₃₁+C₄₁. The level L₄corresponding to the pulse group p₄ and stored in the register 40 a isan inner product of the vector (C₁₁, C₂₁, C₃₁, C₄₁) and a vector (1, −1,1, −1) indicating the pulse group p₄, and is calculated asC₁₁−C₂₁+C₃₁−C₄₁.

The MCU 40 sequentially calculates correlation values T₁ to T₄ of thefour pulse groups p₁ to p₄ correlating with the levels L₁ to L₄accumulated in the shift register 40 a by using the correlator 40 b. Asdepicted in FIG. 5, 4C ₁₁, 4C₂₁, 4C₃₁, and 4C₄₁ are specific contents ofthe correlation values T₁ to T₄ thus calculated. In this case, thecorrelation values T₁ to T₄ reflect changes of capacitances formed atthe intersections of the sensor electrodes 30X₁ to 30X₄ and the sensorelectrode 30Y₁. Accordingly, the MCU 40 can detect the position of thefinger 4 by referring to the correlation values T₁ to T₄ calculated forthe respective sensor electrodes 30Y. More specifically, a regionincluded in the touch surface 3 a and exhibiting a predetermined changeof capacitances or more is determined, and a center position of theregion, for example, is detected as the position of the finger 4.

The detailed description of the position detection process executed bythe MCU 40 for detecting the position of the finger 4 is now completed.Again as depicted in FIG. 4, the logic circuit 41 controls the switch 58x to connect the D terminal to the common terminal at the time ofapplication of the pixel driving voltage Vcom. As a result, the pixeldriving voltage Vcom is supplied to each of the plurality of sensorelectrodes 30X to allow execution of the pixel driving operation.

The reception circuit 44 is a circuit which receives the downlink signalDS transmitted from the active pen 2, or the finger detection signal FDStransmitted from the transmission circuit 42 in response to the controlsignal ctrl_r of the logic circuit 41. More specifically, the receptioncircuit 44 includes an amplification circuit 55, a detection circuit 56,and an analog-digital (AD) converter 57.

The amplification circuit 55 amplifies and outputs the downlink signalDS supplied from the selection circuit 45 or the finger detection signalFDS. The detection circuit 56 is a circuit which generates a voltagecorresponding to a level of an output signal received from theamplification circuit 55. The AD converter 57 is a circuit whichgenerates a digital signal by sampling voltages output from thedetection circuit 56 at predetermined time intervals. The digital signaloutput from the AD converter 57 is supplied to the MCU 40.

The MCU 40 detects the positions of the finger 4 and the active pen 2(coordinates x, y), and acquires data Res transmitted from the activepen 2 based on the digital signal thus supplied. More specifically,concerning the position of the finger 4, the MCU 40 acquires levels L₁to L_(k) corresponding to the pulse groups p₁ to p_(k) for each of thesensor electrode 30Y based on the supplied digital signals. The positionof the finger 4 is detected from the levels l₁ to L_(k) by the methoddescribed above with reference to FIG. 5. Concerning the position of theactive pen 2, as described above, the MCU 40 determines levels ofposition signals at respective intersections of the plurality of sensorelectrodes 30X and 30Y based on the supplied digital signals, anddetects the position of the active pen 2 based on the determined levels.Concerning the data Res, the MCU 40 decodes the digital signals suppliedfrom the reception circuit 44 to acquire the data Res. The MCU 40 isconfigured to output the positions (coordinates x, y) and the data Resthus detected to the host processor 32.

The MCU 40 also determines a contact state between the active pen 2 andthe touch surface 3 a based on writing data included in the acquireddata Res. When it is determined that the active pen 2 is newly broughtinto contact with the touch surface 3 a (i.e., writing pressure changesfrom 0 to positive value), pen-down information IN-PROXY is output tothe host processor 32. When it is determined that the active pen 2 isseparated from the touch surface 3 a (i.e., writing pressure changesfrom positive value to 0), pen-up information OUT-PROXY is output to thehost processor 32. The pen-down information IN-PROXY and the pen-upinformation OUT-PROXY thus output are used by the host processor 32 torecognize a start and an end of a stroke.

The description of the outline of the configuration of the positiondetection system 1 according to the present embodiment is now completed.Detailed contents of the output position determination process and the1/N process described above are sequentially touched upon herein.

Initially, the output position determination process is detailed.

FIG. 6A is a pen position table used for the output positiondetermination process according to the present embodiment, while FIG. 6Bis a touch positon table used for the output position determinationprocess according to the present embodiment. After detecting one or morepositions by the process described above for the active pen 2 or thefinger 4, the MCU 40 uses these tables to determine a position to beoutput to the host processor 32.

As depicted in FIG. 6A, the pen position table is a table which stores acandidate pen position cP[i], a decided pen position fP[i], and a validflag in association with each other. The touch position table is a tablewhich stores a candidate touch position cT[j], a decided touch positionfT[j], a valid flag, and a region type in association with each other.In these tables, i and j are 0 or integers larger than 0. The candidatepen position cP[i] is a position of the active pen 2 detected at S2 inFIG. 3, while the candidate touch position cT[j] is a position of thefinger 4 indicated by entire detection data generated at S7 in FIG. 3.Other parameters will be explained below.

Before touching upon specific contents of the output positiondetermination process, a concept of this process is herein described indetail again with reference to FIG. 1.

In the example depicted in FIG. 1, three types of objects of the activepen 2, the finger 4, and the hand 5 holding the active pen 2 are incontact with the touch surface 3 a. It is preferable, in theory, thatonly the finger 4 of these objects is detected in the position detectionprocess for the finger 4. However, there is a possibility that theactive pen 2 and the hand 5 are also detected. This possibility isproduced by the fact that changes of capacitances of the sensorelectrodes 30X and 30Y may include changes of capacitances formedbetween the sensor electrodes 30X and 30Y and the active pen 2 or thehand 5. In the position detection process for the active pen 2, it ispreferable, in theory, that only the active pen 2 is detected. However,there is a possibility that the hand 5 is also detected. Thispossibility is produced by the fact that the downlink signal DS istransmitted from the active pen 2 to the tablet 3 not only via a route(arrow A in FIG. 1) reaching the touch surface 3 a from the pen tip ofthe active pen 2, but also via a route (arrow B in FIG. 1) passingthrough the hand 5.

After acquiring one or more candidate touch positions by processingdepicted at S5 to S7 in FIG. 3 (or processing depicted at S105 in FIG.2), the MCU 40 initially determines an extent of each candidate touchposition (extent of region exhibiting predetermined change amount ofcapacitance or more). The MCU 40 then excludes a candidate touchposition having an extent determined to have a predetermined size ormore from output targets. In case of the example depicted in FIG. 1, thecontact position of the hand 5 is herein excluded. Thereafter, the MCU40 determines whether or not each of the remaining candidate touchpositions has been detected as the position of the active pen 2 in theposition detection process for the active pen 2 executed immediatelybefore by referring to the pen position table, and excludes thecandidate touch position already detected from the output targets. Incase of the example depicted in FIG. 1, the contact position of theactive pen 2 is herein excluded. In this manner, the candidate touchposition remaining until the end is determined as a position to beoutput to the host processor 32 at S9 in FIG. 3. In this case, thecontact position of the hand 5 and the contact position of the activepen 2 are excluded from the output targets, wherefore only the positionof the finger 4 can be correctly selected and output.

After acquiring one or more candidate pen positions by processingdepicted at S2 in FIG. 3, the MCU 40 determines whether or not each ofthe acquired one or more candidate pen positions has been detected asthe position of the finger 4 or the hand 5 in the position detectionprocess for the finger 4 executed immediately before by referring to thetouch position table. Thereafter, the MCU 40 excludes the candidate penposition determined to have been detected as the position of the hand 5from output targets. In case of the example depicted in FIG. 1, thecontact position of the hand 5 is herein excluded. The candidate penposition not excluded herein, i.e., the candidate pen positiondetermined not to have been detected, and the candidate pen positiondetermined to have been detected as the finger 4 are determined aspositions to be output to the host processor 32 at S4 in FIG. 3. In thiscase, the contact position of the hand 5 is excluded from the outputtargets, wherefore only the position of the active pen 2 can becorrectly selected and output.

According to the position detection process of the present embodiment,therefore, the positions of the active pen 2 and the finger 4 can becorrectly selected and output to the host processor 32. Specificcontents of the output position determination process performed by theMCU 40 with reference to the pen position table and the touch positiontable are hereinafter described in detail.

Each of FIGS. 7 and 8 depicts an example of the output positiondetermination process performed by the MCU 40 with reference to the penposition table and the touch position table.

FIG. 7 depicts an example of a change of each of the pen position tableand the touch position table in time series when position detection ofthe active pen 2 is first performed. The MCU 40 in this example storestwo candidate pen positions cP[0] and cP[1] in a pen position candidatetable as a result of the first position detection process for the activepen 2. Subsequently, the MCU 40 sets corresponding decided pen positionsfP[0] and fP[1] to the candidate pen positions cP[0] and cP[1],respectively, and respective valid flags to “valid.” The MCU 40 suppliesthe respective decided pen positions fP[0] and fP[1] for each of which“valid” has been set to the host processor 32 as detected positions ofthe active pen 2. However, supply of the detected positions to the hostprocessor 32 may be omitted herein.

Subsequently, the MCU 40 performs the first position detection processfor the finger 4, and stores three candidate touch positions cT[0] tocT[2] in a touch position candidate table as a result of the positiondetection process. The MCU 40 then initially detects each extent of thecandidate touch positions cT[0] to cT[2] (extent of region exhibitingpredetermined change amount of capacitance or more). Assuming hereinthat only the candidate touch position cT[1] has a detected extent of apredetermined size or more, and that the other candidate touch positionscT[0] and cT[2] each have a detected extent smaller than thepredetermined size, the MCU 40 sets the decided touch position fT[1] tothe candidate touch position cT[1], the corresponding valid flag to“invalid,” and the corresponding region type to “palm.”

Thereafter, the MCU 40 determines whether or not each of the candidatetouch positions cT[0] and cT[2] having the detected area smaller thanthe predetermined size is substantially equal to each of the decided penpositions fP[0] and fP[1] stored in the pen position candidate table.The state “substantially equal” herein refers to a state in which adistance between one position and the other position is a distance notlonger than a predetermined value sufficiently smaller than the extentof the touch surface 3 a. It is preferable that a specific value of thispredetermined value is equivalent to the sum of lengths of severalpixels, for example.

In case of the example depicted in FIG. 7, the candidate touch positioncT[0] is determined to be substantially equal to the decided penposition fP[0], while the candidate touch position cT[2] is determinednot to be equivalent to each of the decided pen position fP[0] andfP[1]. In this case, the MCU 40 sets the decided pen position fP[2] tothe candidate touch position cT[2], the corresponding valid flag to“valid,” and the corresponding region type to “finger.” However, the MCU40 sets nothing for the decided pen position fP[0] (maintaining initialvalue NULL), and sets the corresponding valid flag to “invalid.” The MCU40 maintains an initial value of the region type corresponding to thedecided pen position fP[0] (sets nothing for region type).

After setting the touch position candidate table as described above, theMCU 40 supplies only the decided touch position fT[2] having the validflag for which “valid” has been set to the host processor 32 as thedetected position of the finger 4. The candidate touch position cT[0]located near the decided pen position fP[O] and having the detectedextent smaller than the predetermined size is not supplied to the hostprocessor 32.

Subsequently, the MCU 40 once resets the pen position candidate table,and then performs the second position detection process for the activepen 2. Assuming herein that none of the active pen 2, the finger 4, andthe hand 5 shifts on the touch surface 3 a, the two candidate penpositions cP[0] and cP[1] are stored in the pen candidate table as aresult of the position detection similarly to the first process.

Thereafter, the MCU 40 determines whether or not each of the acquiredcandidate pen positions cP[0] and cP[1] is substantially equal to eachof the decided touch positions fT[0] to fT[2] stored in the touchposition candidate table. In case of the example depicted in FIG. 7, thedecided touch position fT[0] has been set to NULL at this time.Accordingly, whether or not each of the acquired candidate pen positionscP[0] and cP[1] is substantially equal to each of the decided touchpositions fT[1] and fT[2] is actually determined.

In case of the example depicted in FIG. 7, the candidate pen positioncP[1] is determined to be substantially equal to the decided touchposition fT[1], while the candidate pen position cP[0] is determined notto be equal to each of the decided touch positions fT[0] to fT[2]. Inthis case, the MCU 40 initially sets the decided pen position fP[0] tothe candidate pen position cP[0], and the corresponding valid flag to“valid.” On the other hand, concerning the candidate pen position cP[1],the MCU 40 determines which of “palm” and “finger” is the region type ofthe corresponding decided touch position fT[1]. When the determinationresult indicates “palm,” the MCU 40 sets the decided pen position fP[1]to NULL, and the corresponding valid flag to “invalid.” When thedetermination result is “finger,” the MCU 40 sets the decided penposition fP[1] to the candidate pen position cP[1], and thecorresponding valid flag to “valid.” In case of the example depicted inFIG. 7, the region type of the decided touch position fT[1] is “palm,”wherefore the corresponding decided pen position fP[1] is set to NULL.

FIG. 8 depicts an example of a change of each of the pen position tableand the touch position table in time series when position detection ofthe finger 4 is first performed. The MCU 40 in this example stores threecandidate pen positions cT[0] to cT[2] in a pen position candidate tableas a result of the first position detection process for the finger 4.Subsequently, the MCU 40 detects each extent of the candidate touchpositions cT[0] to cT[2] (extent of region exhibiting predeterminedchange amount of capacitance or more). Assuming herein that only thecandidate touch position cT[1] has a detected extent of a predeterminedsize or more similarly to the example depicted in FIG. 7, the MCU 40initially sets the decided touch position fT[1] to the candidate touchposition cT[1], the corresponding valid flag to “invalid,” and thecorresponding region type to “palm.” Concerning the other two candidatetouch positions cT[0] and cT[2], the MCU 40 sets the decided touchpositions fT[0] and fT[2] to the candidate touch positions cT[0] andcT[2], respectively, the corresponding valid flags to “valid,” and thecorresponding region types to “finger.” The MCU 40 supplies each of thedecided touch positions fT[0] and fT[2] for which “valid” has been setto the host processor 32 as detected positions of the finger 4. However,supply of the detected positions to the host processor 32 may be omittedin this stage.

Subsequently, the MCU 40 performs the first position detection processfor the active pen 2, and stores the two candidate pen positions cP[0]and cP[1] in the pen position candidate table as a result of theprocess. The MCU 40 then determines whether or not each of the acquiredcandidate pen positions cP[0] and cP[1] is substantially equal to eachof the decided pen positions fT[0] to fT[2] stored in the touch positioncandidate table.

In case of the example depicted in FIG. 8, the candidate pen positioncP[0] is determined to be substantially equal to the decided touchposition fT[0], while the candidate pen position cP[1] is determined tobe substantially equal to the decided touch position fT[1].Subsequently, the MCU 40 determines which of “palm” and “finger” is theregion type of each of the decided touch positions fT[0] and fT[1]. Incase of the example depicted in FIG. 8, the region type of the decidedtouch position fT[0] is “finger,” while the region type of the decidedtouch position fT[1] is “palm.”

Concerning the candidate pen positon cP[1] for which “palm” isdetermined as the region type of the corresponding decided touchposition fT[1], the MCU 40 sets the decided pen position fP[1] to NULL,and the corresponding valid flag to “invalid.” Concerning the candidatepen positon cP[0] for which “finger” is determined as the region type ofthe corresponding decided touch position Ft[0], the MCU 40 sets thedecided pen position fP[0] to the candidate pen position cP[0], and thecorresponding valid flag to “valid.” This processing indicates that anerror has been made in the position detection process for the finger 4.The MCU 40 supplies the decided pen position fP[0] for which “valid” hasbeen set to the host process 32 as the detection position of the activepen 2.

Subsequently, the MCU 40 once resets the touch position candidate table,and then performs the second position detection process for the finger4. Assuming herein that none of the active pen 2, the finger 4, and thehand 5 shifts on the touch surface 3 a, the three candidate penpositions cT[0] to cT[2] are stored in the touch candidate table as aresult of the position detection similarly to the first process.

After storing the candidate touch positions cT[0] to cT[2] in the touchposition candidate table, the MCU 40 subsequently detects each extent ofthe candidate touch positions cT[0] to cT[2] (extent of regionexhibiting predetermined change amount of capacitance or more). Assumingherein that only the candidate touch position cT[1] has a detectedextent of the predetermined size or more similarly to the firstdetection, the MCU 40 sets the decided touch position fT[1] to thecandidate touch position cT[1], the corresponding valid flag to“invalid,” and the corresponding region type to “palm.” This processingis similar to the processing performed after the first positiondetection of the finger 4.

Subsequently, the MCU 40 determines whether or not each of the remainingcandidate touch positions cT[0] and cT[2] is substantially equal to eachof the decided pen positions fP[0] and fP[1] stored in the pen positioncandidate table. In case of the example depicted in FIG. 8, thecandidate touch position cT[0] is determined to be substantially equalto the decided pen position fP[0], and the candidate touch positioncT[2] is determined not to be equal to each of the decided pen positionsfP[0] and fP[1] based on this determination. In this case, the MCU 40sets the decided pen position fP[2] to the candidate touch positioncT[2], the corresponding valid flag to “valid,” and the correspondingregion type to “finger.” However, the MCU 40 sets nothing for thedecided pen position fP[0] (maintaining initial value NULL), and setsthe corresponding valid flat to “invalid.” The MCU 40 maintains aninitial value of the region type corresponding to the decided penposition fP[0] (sets nothing for region type).

After setting the touch position candidate table in this manner, the MCU40 supplies only the decided touch position fT[2] for which thecorresponding valid flag is set to “valid” to the host processor 32 asthe detected position of the finger 4.

As described above, the output position determination process accordingto the present embodiment can exclude the contact position of the hand 5from the output targets during the pen position determination process,and exclude the contact positions of the active pen 2 and the hand 5from the output targets during the passive pointer positiondetermination process. Accordingly, even when the contact position ofthe active pen 2 and the contact position of the finger 4 are mutuallymisrecognized in the stage of the candidate pen position and thecandidate touch position, the positions of the active pen 2 and thefinger 4 can be correctly output to the host processor 32 in the finalstage.

The output position determination process performed by the MCU 40 usingthe pen position table and the touch position table is now described inmore detail with reference to the process flow of the MCU 40 again froma different viewpoint.

Each of FIGS. 9 and 10 is a chart depicting details of the flowchartdepicted in FIG. 3. Referring first to FIG. 9, the MCU 40 initiallyexecutes detection of the active pen 2 (S21), and determines whether ornot the active pen 2 has been detected as a result of the detection(S22) to execute the processing at S2 depicted in FIG. 3. When it isdetermined that the active pen 2 has not been detected at S22, theprocess shifts to S51 in FIG. 10 to start the position detection processfor the finger 4.

When it is determined that the active pen 2 has been detected at S22,the MCU 40 executes the pen position determination process depicted atS3 in FIG. 3. More specifically, the MCU 40 initially resets the penposition table (S31). After the reset, the pen position table comes intoa state where no candidate pen position cP[i] is set. Subsequently, theMCU 40 acquires I (I: one or larger integer) candidate pen positionscP[i] (i: 0 to I−1) detected at S21, and adds the acquired candidate penpositions cP[i] to the pen position table (S32). Thereafter, the MCU 40sequentially performs processing at S34 to S36 for all the candidate penpositions cP[i] (S33).

More specifically, the MCU 40 initially determines whether or not adecided touch position fT[j] equal to the candidate pen position cP[i]has been stored in the touch position table (S34). When it is determinedthat the decided touch position fT[j] equal to the candidate penposition cP[i] has been stored, it is determined which of “finger” and“palm” is the region type of this decided touch position stored in thetouch position table (S35).

When it is determined that the decided touch position fT[j] equal to thecandidate pen position cP[i] has not been stored at S34, and that it isdetermined that the region type is “finger” at S35, the MCU 40 sets thedecided pen position fP[i] to the candidate pen position cP[i], and thecorresponding valid flag to “valid” (S36). When it is determined thatthe region type is “palm” at S35, processing at S36 is not performed. Asa result, the corresponding decided pen position fP[i] is set to NULL,while the corresponding valid flag is set to “invalid.”

When the processing at S34 to S36 is completed for all the candidate penpositions cP[i], the MCU 40 outputs only the decided pen positon fP[i]for which the corresponding valid flag has been set to “valid” to thehost processor 32 as the detected position of the active pen 2 (S4), andthen starts the position detection process for the finger 4.

More specifically, as depicted in FIG. 10, the MCU 40 executes detectionof the finger 4 (S51), and determines whether or not the finger 4 hasbeen detected as a result of the detection (S52) to execute theprocessing at S5 to S7 depicted in FIG. 3. While the processing at S5 toS7 is executed herein, processing at S105 in FIG. 2 may be executedinstead. In this case, however, the processing at S2 to S4 needs to besuccessively performed twice to obtain a sufficient detection rate ofthe active pen 2. When it is determined that the finger 4 has not beendetected at S52, the process shifts to S21 in FIG. 9 to start theposition detection process for the active pen 2.

When it is determined that the finger 4 has been detected at S52, theMCU 40 executes the passive pointer position determination processdepicted at S8 in FIG. 3. More specifically, the MCU 40 initially resetsthe touch position table (S81). After the reset, the touch positiontable comes into a state where no candidate touch position cT[j] is set.Subsequently, the MCU 40 acquires J (J: one or larger integer) candidatetouch positions cT[j] (j: 0 to J−1) detected at S51, and adds theacquired candidate touch positions cT[j] to the touch position table(S82). Thereafter, the MCU 40 sequentially performs processing at S84 toS87 for all the candidate pen positions cT[j] (S83).

More specifically, the MCU 40 initially calculates an area of thecandidate touch position cT[j]. The area to be calculated herein is anarea of a region including the candidate touch position cT[j], andexhibiting a predetermined change amount of capacitance or more. Then,the MCU 40 determines whether or not the calculated area is apredetermined size or larger (S84).

When it is determined that the area is the predetermined size or largerat S84 (i.e., area is determined to be large), the MCU 40 sets thedecided touch position fT[j] to the candidate touch position cT[j], andthe corresponding valid flag to “invalid,” and the corresponding regiontype to “palm” (S85).

When it is determined that the area is not the predetermined size orlarger at S84 (i.e., area is determined to be small), the MCU 40subsequently determines whether or not a decided pen position fP[i]substantially equal to the candidate touch position cT[j] has beenstored in the pen position table (S86). When it is determined thedecided pen position fP[i] substantially equal to the candidate touchposition cT[j] has not been stored, the MCU 40 sets the decided touchposition fT[j] to the candidate touch position cT[j], the correspondingvalid flag to “valid,” and the corresponding region type to “finger”(S87). When it is determined that the decided pen position fP[i]substantially equal to the candidate touch position cT[j] has beenstored at S86, the MCU 40 does not perform processing at S87. As aresult, the corresponding decided touch position fT[j] is set to NULL,and the corresponding valid flag is set to “invalid.”

When the processing at S15 to S18 is completed for all the candidatetouch positions cT[j], the MCU 40 outputs only the decided touch positonfT[j] for which the corresponding valid flag has been set to “valid” tothe host processor 32 as the detected position of the finger 4 (S9), andthen returns to S2 to start the position detection process for theactive pen 2.

More detailed description again concerning the output positiondetermination process performed by the MCU 40 using the pen positiontable and the touch position table is now completed with reference tothe process flow of the MCU 40. The output position determinationprocess according to the present embodiment may be modified in variousmanners. Hereinafter described are first to fourth modified examples ofthe output position determination process according to the presentembodiment.

The first modified example relates to the pen position determinationprocess. The MCU 40 according to the present modified example isconfigured to output a position corresponding to the highest level ofthe downlink signal DS to the host processor 32 as the position of theactive pen 2 when a plurality of positions corresponding to apredetermined level or higher of the downlink signal DS are detected. Incase of the example depicted in FIG. 7, the level of the downlink signalDS at the candidate pen position cP[1] detected based on the downlinksignal DS received via the hand 5 of the user is generally lower thanthe level of the downlink signal DS at the candidate pen position cP[0]detected based on the downlink signal DS directly received from the penelectrode of the active pen 2. Accordingly, the MCU 40 outputs thecandidate pen position cP[0] to the host processor 32 as the position ofthe active pen 2. This result is similar to the corresponding result ofthe embodiment described above. It is therefore concluded that the MCU40 of the present modified example can also correctly output theposition of the active pen 2 to the host processor 32.

The second modified example also relates to the pen positiondetermination process. The MCU 40 according to the present modifiedexample is configured to detect the position of the active pen 2 basedon an area of a region corresponding to the downlink signals DS eachcorresponding to a predetermined level or higher and successivelylocated when a plurality of positions of the downlink signals DS havingthe predetermined level or higher and located away from each other aredetected. More specifically, a position of a smaller area is detected asthe position of the active pen 2. In case of the example depicted inFIG. 7, the area of the candidate pen position cP[1] detected based onthe downlink signal DS received via the hand 5 of the user is largerthan the area of the candidate pen position cP[0] detected based on thedownlink signal DS received directly from the pen electrode of theactive pen 2. Accordingly, the MCU 40 outputs the candidate pen positioncP[0] to the host processor 32 as the position of the active pen 2. Thisresult is also similar to the result of the embodiment described above.It is therefore concluded that the MCU 40 of the present modifiedexample can also correctly output the position of the active pen 2 tothe host processor 32.

The third modified example relates to the passive pointer positiondetermination process. The MCU 40 of the present modified example isconfigured to change a predetermined size corresponding to a referencefor determination at S15 depicted in FIG. 10 (palm determination) inaccordance with whether or not the position of the active pen 2 has beendetected by the position detection process for the active pen 2performed immediately before. More specifically, the MCU 40 isconfigured to reduce the predetermined size when one or more penpositions are output in the pen detection process (see FIG. 3) performedimmediately before. For example, the predetermined size is set to 20 mmwhen the position of the active pen 2 is not detected in the positiondetermination process for the active pen 2 performed immediately before,while the predetermined size is set to 16 mm when one or more positionsof the active pen 2 are detected in the position determination processfor the active pen 2 performed immediately before. This changing processis performed to more rapidly distinguish between the active pen 2 andthe hand 5 in the state that the active pen 2 has been detected. Morespecifically, a certain short period is required to bring the hand 5into contact with the touch surface 3 a, wherefore a small contact areamay be produced between the hand 5 and the touch surface 3 a at acertain time during this period. Accordingly, misrecognition of thecontact position of the hand 5 as the contact position of the finger 4may be caused at the time of determination of the palm or the fingerbased on determination of the area during the position detection processfor the finger 4. According to the present modified example, however,the possibility of the misrecognition can decrease by reduction of thepredetermined size as described above in the state that the active pen 2has been detected.

According to the position detection process for the active pen 2described above, the position of the active pen 2 is detectable even ina state of non-contact between the active pen 2 and the touch surface 3a (hover state). More specifically, the position of the active pen 2even in the hover state is detectable based on the downlink signal DSdetected by the MCU 40 when the active pen 2 approaches the touchsurface 3 a to a certain degree or more from the touch surface 3 a.According to the third modified example, the predetermined size can bereduced during the hover state of the active pen 2 approaching the touchsurface 3 a, wherefore the active pen 2 comes into contact with thetouch surface 3 a with a reduced possibility of the foregoingmisrecognition.

FIG. 11 is a flowchart depicting the pointer position detection processperformed by the controller 31 according to the fourth modified example.This figure depicts a modified example of the flowchart depicted in FIG.9.

The flowchart of FIG. 11 is different from the flowchart of FIG. 9 inthat step S37 is executed after determination as “palm” at S35. Morespecifically, the MCU 40 of the present modified example determineswhether or not the pen position currently detected at S35 (morespecifically, candidate pen position cP[i]) is present near the palmregion (i.e., which of “finger” and “palm” is the region type stored inthe touch position table and associated with the decided touch positionfT[j] substantially equal to the candidate pen position cP[i]). When itis determined that the current pen position is present near the palmregion (i.e., region type is determined to be “palm”), it is determinedwhich of valid (writing pressure>0) and invalid (printing pressure=0) isselected as a writing pressure (writing pressure previously detected)indicated by printing pressure data included in the data Res output inthe previous pen detection process (S37). When it is determined that theprinting pressure is valid, the process shifts to S36 to set the decidedpen position fP[i] to the candidate pen position cP[i], and set thecorresponding valid flag to “valid” (S36). When it is determined thatthe writing pressure is invalid, processing at S36 is not performed. Inthis case, the corresponding decided pen position fP[i] is set to NULL,while the corresponding valid flag is set to “invalid.”

According to the fourth modified example, disappearance of a drawingline near the palm region can be prevented during input operation by theuser using the active pen 2. More specifically, according to the processflow of FIG. 9, determination as “palm” is made at S35 when the pen tipapproaches the palm area during input operation by the user using theactive pen. In this case, the decided pen position fP[i] is not set tothe candidate pen position cP[i]. As a result, coordinates are notoutput to the host processor 32, wherefore a drawing line is broken. Itis preferable, however, that no break of the drawing line is producedduring continuous input operation by the user even when the pen tipapproaches the palm region. According to the fourth modified example, itis determined at S37 whether the writing pressure previously detected isvalid or invalid, wherefore whether or not the user continuouslyperforms input operation can be determined. Accordingly, coordinateoutput to the host processor 32 is allowed to continue during continuousinput operation by the user, wherefore disappearance of a drawing linenear the palm region is avoidable during input operation by the userusing the active pen 2.

Described hereinafter in detail is the 1/N process. In the followingdescription, problems arising from the related art concerning the 1/Nprocess, and advantageous effects produced by introduction of the 1/Nprocess are again described in more detail, and then contents of the 1/Nprocess are described in detail.

FIG. 12A is a chart depicting a control sequence of a pointer positiondetection process according to the related art of the presentdisclosure, while FIG. 12B is a chart depicting a control sequence of apointer position detection process according to the present embodiment.In these charts, “T” indicates a period in which the MCU 40 performs theposition detection process for the finger 4, while “P” indicates aperiod in which the MCU 40 performs the position detection process forthe active pen 2.

As depicted in FIG. 12A, the MCU 40 according to the related art of thepresent disclosure performs the position detection process for theactive pen 2 successively twice. This process requires 3 millisecondsper one process. The MCU 40 subsequently performs the position detectionprocess for the finger 4 once. This process requires 2 milliseconds perone process. The MCU 40 is configured to repeat the position detectionprocess for the finger 4 and the active pen 2 in this pattern. Thedetection rate of the finger 4 in this case is 125 (=1/8×1000)times/sec, while the detection rate of the active pen 2 in this case is250 (=2/8×1000) times/sec. In this case, the detection rate of theactive pen 2 improves. According to this position detection process,however, detection intervals of the active pen 2 are not regularintervals, wherefore an unnatural drawing result is produced in adrawing application which operates based on an expectation thatcoordinate data indicating the active pen 2 and sequentially output fromthe sensor controller 31 is transmitted at regular intervals in view oftime, for example.

However, the MCU 40 of the present embodiment executes the 1/N processof the position detection process (first detection process) for thefinger 4 (first pointer) at a rate of 250 (=1/4×1000) (first detectionrate) as depicted in FIG. 12B. In FIG. 12B, N is set to 2, in which casea time required for executing the 1/N process is ½ of the time requiredfor executing the position detection process for the finger 4 accordingto the example depicted in FIG. 12A, i.e., 1 millisecond. Thereafter,the MCU 40 acquires partial detection data indicating whether or not thefinger 4 is present based on the 1/N process, and retains the partialdetection data in the shift register 40 a depicted in FIG. 5 (firstdetection step up to this processing). The shift register 40 a isconfigured to store N partial detection data, and delete partialdetection data acquired N times before at the time of writing newpartial detection data to the shift register 40 a.

The MCU 40 further combines (N−1) partial detection data alreadyretained in the memory and partial detection data newly retained everytime new partial detection data is retained in the memory to generateentire detection data indicating whether or not the finger 4 is presentfor the entire touch surface 3 a (combining). The generated entiredetection data is subjected to the correlation value calculation process(correlation value calculation step) described with reference to FIG. 5,and output from the MCU 40 to the host processor 32 at the firstdetection rate (250 times/sec) as the passive pointer position(reporting).

The 1/N process is executed at predetermined intervals (morespecifically, intervals of 3 milliseconds). The entire positiondetection process (second detection process) for the active pen 2(second pointer) is executed only once at each interval (seconddetection). Accordingly, the detection rate of the position of theactive pen 2 (second detection rate) is equal to the first detectionrate (250 times/sec) described above. Even in the state that detectionof the active pen 2 is executed at regular intervals, the detection rateof the active pen 2 in this case is equalized with the detection rate ofthe active pen 2 of the example depicted in FIG. 12A.

According to the pointer position detection process of the presentembodiment, the position detection process for the finger 4 is dividedinto N partial processes. In this case, detection of the active pen 2can be executed at regular intervals while maintaining the detectionrates of both the active pen 2 and the finger 4. Accordingly, theproblems described above are not produced. The contents of the 1/Nprocess are hereinafter described in detail.

Described hereinafter are first to fifth examples of the contents of the1/N process. The 1/N process in each of the first to fourth examplesdetects 1/N of the entire touch surface 3 a (i.e., detects changes ofcapacitances at intersections of sensor electrodes 30X and sensorelectrodes 30Y), and uses substantially 1/N of the plurality of sensorelectrodes 30X (first electrodes) (see FIGS. 14A and 14B and 16A and 16Breferred to below), for example, or substantially 1/N of the pluralityof sensor electrodes 30Y (second electrodes) (see FIGS. 15A and 15B and17A and 17B referred to below), for example. In this case, substantially1/N is the number of the sensor electrodes 30X or the sensor electrodes30Y adjusted to an integer when 1/N is not an integer in each process.On the other hand, the 1/N process in the fifth example uses 1/N part ofthe finger detection signal FDS (more specifically, M of N×M (M=K/N)pulses constituting each of the signals s₁ to s_(k) described above)(see FIGS. 18A and 18B referred to below). Each of the examples ishereinafter detailed. Described herein is an example of N=2 and use ofthe 16×16 sensor 30. However, the same description is applicable to thecase of N≥3 or the sensor 30 of a size other than 16×16.

Initially, FIG. 13 is a diagram depicting an example of the fingerdetection signal FDS used together with the 16×16 sensor 30. As depictedin this figure, the finger detection signal FDS in this case isconstituted by 16 pulse groups p₁ to p₁₆. Each of the pulse groups p₁ top₁₆ includes 16 pulses expressed as “1” or “−1.”

As described above, the MCU 40 and the logic circuit 41 are configuredto repeatedly perform, for the respective sensor electrodes 30Y, theoperation for selecting the one sensor electrode 30Y, and causing thetransmission circuit 42 to sequentially input the respective pulsegroups p_(n) (n=1 to 16) to the respective sensor electrodes 30X.Accordingly, assuming that a time required for processing the one pulsegroup p_(n) is t, a time required for performing the position detectionprocess for the finger 4 (in this example, position detection processexecuted at S105 depicted in FIG. 2) is t×16 (=total number of pulsegroups p_(n))×16 (=total number of sensor electrodes 30Y).

FIGS. 14A and 14B are diagrams depicting the first example of thecontents of the 1/N process. FIG. 14A depicts a first process, whileFIG. 14B depicts a second process. This example performs the 1/N processusing the eight sensor electrodes 30X different from each other in eachof the first process and the second process. More specifically, everyother sensor is selected from the 16 sensor electrodes 30X arranged inthe X direction, and used for the first process, while the remainingsensor electrodes 30X are used for the second process.

According to the first example, the number of the sensor electrodes 30Xto which the finger detection signal FDS is input in one process iseight, wherefore the finger detection signal FDS can be constituted byonly the eight pulse groups p₁ to p₈. Accordingly, the time required forperforming one process is t×8 (=total number of pulse groups p_(n))×16(=total number of sensor electrodes 30Y), wherefore one process can becompleted in ½ of the time required for the position detection processof the example depicted in FIG. 2 or FIG. 12A.

Moreover, according to the first example, all the sensor electrodes 30Xare covered by the first and second processes. Accordingly, the MCU 40can generate entire detection data indicating whether or not the finger4 is present for the entire touch surface 3 a by combining partialdetection data retained in the shift register 40 a (see FIG. 5) as aresult of the first process, and partial detection data retained in theshift register 40 a as a result of the second process.

Furthermore, according to the first example, the order of the firstprocess and the second process is not particularly limited. Accordingly,at the time of acquisition of new partial detection data, the MCU 40 cangenerate entire detection data by combining the new partial detectiondata with (N−1) partial detection data already stored in the shiftregister 40 a every time the 1/N process is performed. Morespecifically, entire detection data can be generated not only bycombining the partial detection data retained in the shift register 40 aas a result of the first process and the partial detection data retainedin the shift register 40 a as a result of the second process executedimmediately after the first process, but also by combining the partialdetection data retained in the shift register 40 a as a result of thesecond process and the partial detection data retained in the shiftregister 40 a as a result of the first process executed immediatelyafter the second process. Accordingly, the detection result of thefinger 4 can be output at a twice higher detection rate than thedetection rate of the finger 4 of the example depicted in FIG. 2 or FIG.12A.

FIGS. 15A and 15B are diagrams depicting the second example of thecontents of the 1/N process. FIG. 15A depicts a first process, whileFIG. 15B depicts a second process. This example performs the 1/N processusing the eight sensor electrodes 30Y different from each other in eachof the first process and the second process. More specifically, everyother sensor is selected from the 16 sensor electrodes 30Y arranged inthe Y direction, and used for the first process, while the remainingsensor electrodes 30Y are used for the second process.

According to the second example, the number of the sensor electrodes 30Yselected in one process is eight. Accordingly, the time required forperforming one process is t×16 (=total number of pulse groups p_(n))×8(=total number of sensor electrodes 30Y), wherefore one process can becompleted in ½ of the time required for the position detection processof the example depicted in FIG. 2 or FIG. 12A.

Moreover, according to the second example, all the sensor electrodes 30Yare covered by the first and second processes similarly to the aboveexample. Accordingly, similarly to the first example, the MCU 40 cangenerate entire detection data indicating whether or not the finger 4 ispresent for the entire touch surface 3 a by combining partial detectiondata retained in the shift register 40 a as a result of the firstprocess, and partial detection data retained in the shift register 40 aas a result of the second process.

Furthermore, according to the second example, the order of the firstprocess and the second process is not particularly limited similarly tothe above example. Accordingly, the detection result of the finger 4 canbe output at a twice higher detection rate than the detection rate ofthe finger 4 of the example depicted in FIG. 2 or FIG. 12A similarly tothe first example.

FIGS. 16A and 16B are diagrams depicting the third example of thecontents of the 1/N process. FIG. 16A depicts a first process, whileFIG. 16B depicts a second process. This example performs the 1/N processusing the eight sensor electrodes 30X different from each other in eachof the first process and the second process similarly to the firstexample. However, in the present example, eight sensors are sequentiallyselected from one end of the arranged 16 sensor electrodes 30X, and usedfor the first process, while the remaining sensor electrodes 30X areused for the second process.

According to the third example, one process can be completed in ½ of thetime required for the position detection process of the example depictedin FIG. 2 or FIG. 12A for a reason similar to the reason of the firstexample. Moreover, entire detection data indicating whether or not thefinger 4 is present can be generated for the entire touch surface 3 a.Furthermore, a detection result of the finger 4 can be output at a twicehigher detection rate than the detection rate of the finger 4 of theexample depicted in FIG. 2 or FIG. 12A.

FIGS. 17A and 17B are diagrams depicting the fourth example of thecontents of the 1/N process. FIG. 17A depicts a first process, whileFIG. 17B depicts a second process. This example performs the 1/N processusing the eight sensor electrodes 30Y different from each other in eachof the first process and the second process similarly to the secondexample. However, in the present example, eight sensors are sequentiallyselected from one end of the arranged 16 sensor electrodes 30Y, and usedfor the first process, while the remaining sensor electrodes 30Y areused for the second process.

According to the fourth example, one process can be completed in ½ ofthe time required for the position detection process of the exampledepicted in FIG. 2 or FIG. 12A for a reason similar to the reason of thesecond example. Moreover, entire detection data indicating whether ornot the finger 4 is present can be generated for the entire touchsurface 3 a. Furthermore, a detection result of the finger 4 can beoutput at a twice higher detection rate than the detection rate of thefinger 4 of the example depicted in FIG. 2 or FIG. 12A.

FIGS. 18A and 18B are diagrams depicting the fifth example of thecontents of the 1/N process. FIG. 18A depicts a first process, whileFIG. 18B depicts a second process. In this example, only the half of the16 pulse groups p₁ to p₁₆ are used in the first process, while theremaining pulse groups are used in the second process. Morespecifically, the pulse groups p₁ to p₈ are used in the first process,while the pulse groups p₉ to p₁₆ are used in the second process.

According to the fifth example, only the eight pulses are input to eachof the sensor electrodes 30X in one process. In this case, the timerequired for performing one process is t×8 (=total number of pulsegroups p_(n))×16 (=total number of sensor electrodes 30Y), wherefore onedetection operation can be completed in ½ of the time of the positiondetection process of the example depicted in FIG. 2 or FIG. 12A.

Moreover, according to the fifth example, all the 16 pulse groups p₁ top₁₆ are covered by the first and second processes. Accordingly,similarly to the first to fourth examples, the MCU 40 can generateentire detection data indicating whether or not the finger 4 is presentfor the entire touch surface 3 a by combining partial detection dataretained in the shift register 40 a as a result of the first process,and partial detection data retained in the shift register 40 a as aresult of the second process.

Furthermore, the order of the first process and the second process isnot particularly limited in the fifth example similarly to the aboveexamples. Accordingly, the detection result of the finger 4 can beoutput at a twice higher detection rate than the detection rate of thefinger 4 of the example depicted in FIG. 2 or FIG. 12A.

FIGS. 19 and 20 are diagrams each depicting an example of specificstorage contents of the shift register 40 a (see FIG. 5) in the fifthexample. These figures each indicate the storage contents of the shiftregister 40 a arranged in correspondence with the respective sensorelectrodes 30Y for easy understanding. Numerical values depicted in thesensor 30 in these figures indicate capacitances at the respectiveintersections of the sensor electrodes 30X and 30Y. A method forgenerating the entire detection data in the fifth example is hereinafterspecifically described with reference to FIGS. 19 and 20.

FIG. 19 depicts storage contents of the shift register 40 a immediatelyafter completion of the first process. In the first process, the levelsL₁ to L₈ are stored in the shift register 40 a for each of the sensorelectrodes 30Y. At the time of completion of the first process for oneof the sensor electrodes 30Y, there remain the levels L₉ to L₁₆ storedin the shift register 40 a by the second process performed immediatelybefore the first process for the corresponding sensor electrode 30Y asdepicted in FIG. 19. Accordingly, the MCU 40 combines partial detectiondata expressed by the levels L₁ to L₈ newly stored, and partialdetection data expressed by the levels L₉ to L₁₆ remaining in the shiftregister 40 a into one entire detection data, and calculates thecorrelation values described above using the entire detection data. Inthis manner, the MCU 40 can output coordinates indicating the positionof the finger 4 to the host processor 32 at the time of completion ofthe first detection operation.

FIG. 20 depicts storage contents of the shift register 40 a immediatelyafter completion of the second process. In the second process, thelevels L₉ to L₁₆ are stored in the shift register 40 a for each of thesensor electrodes 30Y. At the time of completion of the second processfor one of the sensor electrodes 30Y, there remain the levels L₁ to L₈stored in the shift register 40 a by the first process performedimmediately before the second process for the corresponding sensorelectrode 30Y as depicted in FIG. 20. Accordingly, the MCU 40 combinespartial detection data expressed by the levels L₉ to L₁₆ newly stored,and partial detection data expressed by the levels L₁ to L₈ remaining inthe shift register 40 a into one entire detection data, and calculatesthe correlation values described above using the entire detection data.In this manner, the MCU 40 can output coordinates indicating theposition of the finger 4 to the host processor 32 also at the time ofcompletion of the second detection operation.

As described above, the pointer position detection process according tothe present embodiment executes the position detection process for thefinger 4 after dividing the process into N parts. Accordingly, detectionof the active pen 2 is achievable at regular intervals while maintainingsufficient detection rates of both the active pen 2 and the finger 4.Accordingly, this detection process overcomes the problem of theunnatural drawing result produced in the drawing application whichoperates based on the expectation that coordinate data indicating theactive pen 2 and sequentially output from the sensor controller 31 istransmitted at regular intervals in view of time, for example. Moreover,according to the position detection process of the present embodiment,the finger 4 is detectable at a higher detection rate than that of therelated art.

The position detection system 1 according to a second embodiment of thepresent disclosure is hereinafter described. The position detectionsystem 1 according to the present embodiment has a function ofpreventing formation of an unnecessary line caused by presence of aghost position described above, as well as the functions of the positiondetection system 1 of the first embodiment. Configurations identical tothe corresponding configurations of the first embodiment are givenidentical reference numbers, and differences from the first embodimentare hereinafter chiefly described.

FIG. 22 is a view illustrating an example of a state of use of theposition detection system 1 according to the present embodiment. FIG. 23is a diagram explaining an operation of the host processor 32 accordingto the related art of the present embodiment. An object of the presentembodiment is hereinafter initially described with reference to FIGS. 22and 23, and subsequently an operation of the sensor controller 31according to the present embodiment is touched upon.

As illustrated in FIG. 22, during input operation using the active pen2, there occurs such a situation where the user brings the hand(hereinafter referred to as left hand) opposite to the hand (hereinafterreferred to as right hand) holding the active pen 2 into contact withthe touch surface 3 a. In this case, the contact position of the lefthand (palm region Palm in the figure) is excluded from both the touchposition and the pen position by the process described in the firstembodiment. Apart from this contact position, a pen position (ghostposition G depicted in the figure) may be detected below the left arm.This pen position is produced when a current path CR (current pathextending from pen electrode of active pen 2 toward sensor electrodes30X, entering left arm, passing through human body, and returning toactive pen 2) is formed as depicted in the figure. In this case, atransmission signal of the active pen 2 may be detected below the leftarm. While the example of the sensor electrodes 30X is depicted in FIG.22, this situation is also applicable to the sensor electrodes 30Y.

The level of the signal detected at the ghost position G is lower thanthe level of the signal detected at the contact position of the activepen 2 (pen position P depicted in the figure). Moreover, the active pen2 detectable by the tablet 3 at a time is normally only one pen.Accordingly, the ghost position G produces no problem as long as theactive pen 2 contacts the touch surface 3 a. However, when the activepen 2 suddenly shifts from a bezel region 3 b of the tablet 3 to theinside of the touch surface 3 a along an arrow A depicted in the figure,for example, the sensor controller 31 may detect the ghost position Gbefore detection of the actual pen position P.

FIG. 23 depicts the ghost position G initially detected in thissituation as the (n−1)th decided pen position fP_(n−1), and the penposition P subsequently detected as the nth decided pen position fP_(n).When the decided pen positions fP_(n−1) and fP_(n) are successivelydetected, the host processor 32 having received these pen positionsdraws a line segment L between these pen positions as depicted in FIG.23. However, this drawing of the line segment L is not intended by theuser, wherefore formation of the line segment L needs to be prevented.The object of the present embodiment therefore is to prevent formationof the line segment L. An operation of the sensor controller 31 forachieving this object is hereinafter described in detail with referenceto FIG. 24.

FIG. 24 is a flowchart depicting a pointer position detection processexecuted by the sensor controller 31 according to the presentembodiment. This figure depicts S101 to S107 added to the pen detectionsteps depicted in FIG. 3. The operation of the sensor controller 31according to the present embodiment is hereinafter described in detailwith reference to FIG. 24 and again FIG. 23.

The sensor controller 31 (more specifically, MCU 40 depicted in FIG. 4)according to the present embodiment determines the pen position at S3,and then determines whether or not the touch position, for which theregion type is determined to be palm, has been detected in the touchdetection process (see FIG. 3) performed immediately before (S101). Whenit is determined that the touch position has not been detected, thesensor controller 31 stores the determined pen position separately fromthe pen position table described above (S107), and performs the outputprocess at S4. When it is determined that the touch position has beendetected, the sensor controller 31 subsequently determines whether ornot the pen position stored previously at S106 (previous pen position)lies within a predetermined region formed based on the detected palmregion Palm (S102).

FIG. 23 depicts an example of the predetermined region. The sensorcontroller 31 is configured to acquire an extent of the palm region Palmfrom the correlation values described with reference to FIG. 5, andfurther acquire a cross region (cross region XR) within the touchsurface 3 a as a region corresponding to the sensor electrodes 30X and30Y and passing through the inside of the palm region Palm based on theextent thus acquired. The predetermined region is constituted by thecross region XR acquired in this manner.

Returning to FIG. 24, the sensor controller 31 subsequently compares alevel of a transmission signal (more specifically, position signaldescribed above) transmitted from the active pen 2 and corresponding tothe pen position (current pen position) determined currently at S3 witha predetermined threshold, and determines whether to output the detectedpen position based on a result of the comparison (S103). Morespecifically, when it is determined that the level of the transmissionsignal is lower than the predetermined threshold (low), the processproceeds to processing after S4, and shifts to the touch detectionprocess depicted in FIG. 3. When it is determined that the level of thetransmission signal is the predetermined threshold or higher (high), theprocess proceeds to S104. The threshold used at S103 herein is set to avalue lower than the predetermined value used for detecting the positionof the active pen 2 by the MCU 40. The processing at S103 corresponds toprocessing for increasing the threshold for detecting the pen positionas a post process. In this manner, reduction of the possibility ofdetection of the ghost position G is achievable within the cross regionXR.

Thereafter, the sensor controller 31 calculates a distance between theprevious pen position and the current pen position. This distancecorresponds to the distance between the decided pen positions fP_(n−1)and fP_(n) in FIG. 23. The sensor controller 31 subsequently determineswhether the distance exceeds a predetermined value (long) or not (short)(S104). When it is determined that the distance exceeds thepredetermined value, the sensor controller 31 sequentially outputs, tothe host processor 32, pen-up information OUT-PROXY indicating that theactive pen 2 is separated from the touch surface 3 a, and pen-downinformation IN-PROXY indicating that the active pen 2 is in contact withthe touch surface 3 a (steps S105 and S106). When it is determined thatthe distance does not exceed the predetermined value at S104 and aftercompletion of S106, the sensor controller 31 stores the determined penposition separately from the pen position table described above (S107),and performs the output process at S4.

As described above, the pointer position detection process of thepresent embodiment can output the pen-up information OUT-PROXY to thehost processor 32 when the distance between the pen position currentlydetected and the pen position previously detected exceeds thepredetermined value. In this case, the host processor 32 determines thecurrent pen position and the previous pen position belong to differentstrokes. Accordingly, formation of an unnecessary line segment caused bypresence of the ghost position G, such as the line segment L depicted inFIG. 23, can be prevented.

It should be understood that the present disclosure is not limited tothe specific preferred embodiments described herein. Needless to say,the disclosure may be practiced in various modes without departing fromthe subject matters of the present disclosure.

For example, the pointer position detection process according to thepresent embodiments may be practiced in preferred modes other than themodes described herein. Specific examples of other modes are hereinafterdescribed.

FIG. 21A is a chart depicting a control sequence of a position detectionprocess according to a first modified example of the presentembodiments. The MCU 40 of the present modified example is configured toperform a ½ process at predetermined intervals, and combine partialdetection data obtained in the ½ process and partial detection dataobtained in the process performed immediately before the ½ process togenerate entire detection data FM1, FM2, FM3, FM4 and others at a twicehigher rate. In each of the intervals, either the position detectionprocess for the active pen 2 or the pixel driving operation may beexecuted, or both the position detection process for the active pen 2and the pixel driving operation may be executed in a time-dividedmanner.

In association with the first modified example, the MCU 40 may determinewhether to execute the position detection process for the finger 4 atthe predetermined intervals, and execute the position detection processfor the finger 4 as a process divided into N parts only when theposition detection process for the finger 4 is determined to beexecuted. When it is determined that the process is not executed, S5 toS7 depicted in FIG. 3 are replaced with S103 depicted in FIG. 2. In thismanner, the method for executing the position detection process for thefinger 4 can be switched in accordance with the necessity of executionof the position detection process for the active pen 2 or the pixeldriving operation.

FIG. 21B is a chart depicting a control sequence of the positiondetection process according to a second modified example of the presentembodiments. The MCU 40 of the present modified example is configured toperform the position detection process for the finger 4 successivelyexecuted (without providing intervals) but divided into two parts. Inthis manner, as depicted in this figure, the entire detection data FM1,FM2, FM3, FM4 and others can be generated at a twice higher detectionrate than the rate of the position detection process for the finger 4completed by one process.

FIG. 21C is a chart depicting a control sequence of the positiondetection process according to a third modified example of the presentembodiments. The MCU 40 of the present modified example is configured toperform the position detection process for the finger 4 successivelyexecuted (without providing intervals) but divided into three parts. Inthis manner, as depicted in this figure, the entire detection data FM1,FM2, FM3, FM4 and others can be generated at a three times higherdetection rate than the rate of the position detection process for thefinger 4 completed by one process.

Moreover, while the example which divides the position detection processfor the finger 4 (passive pointer) into a plurality of processes hasbeen described in the embodiments, the position detection process forthe active pen 2 may be similarly divided into a plurality of processes.

According to the embodiments described above, the MCU 40 always uses thepen position table and the touch position table for performing theoutput position determination process. However, when only one positionis detected at S21 in FIG. 9, for example, this position may bedetermined as a pen position to be output, and the pen positiondetermination process at S3 may be skipped. Similarly, when only oneposition is detected at S51 in FIG. 9, for example, this position may bedetermined as a passive pointer position to be output, and the passivepointer position determination process at S8 may be skipped.

According to the embodiments described above, the logic circuit 41 andthe MCU 40 repeatedly perform, for the respective sensor electrodes 30Y,the operation for selecting the one sensor electrode 30Y, and causingthe transmission circuit 42 to sequentially input the pulse groups p₁ top_(k) described above to the respective sensor electrodes 30X. However,the reception circuit 44 may be provided for each of the sensorelectrodes 30Y to execute the processes for the respective sensorelectrodes 30Y in parallel. In this case, it is difficult to produce theadvantage of reduction of the time required for the position detectionprocess in the second and fourth examples using the contents of the 1/Nprocess depicted in FIGS. 15A and 15B and FIGS. 17A and 17B. However,the one reception circuit 44 can be shared by the two sensor electrodes30Y, wherefore a new advantage of reduction of a circuit scale of thereception circuits 44 is achievable in comparison with the configurationproviding the reception circuit 44 for each of the sensor electrodes30Y.

What is claimed is:
 1. A pointer position detection method for detectinga position of a pointer present within a predetermined region, themethod comprising: performing 1/N of a first detection process at afirst detection rate; acquiring partial detection data that indicateswhether a first pointer is detected based on the performing the 1/N ofthe first detection process; storing the partial detection data in amemory; combining (N−1) partial detection data already stored in thememory and the partial detection data responsive to the storing thepartial detection data in the memory; generating detection data thatindicates whether the first pointer is detected throughout thepredetermined region; and outputting the detection data at the firstdetection rate.
 2. The pointer position detection method according toclaim 1, wherein: the performing the 1/N of the first detection processdetects 1/N of the predetermined region.
 3. The pointer positiondetection method according to claim 2, wherein: a plurality ofelectrodes is provided in the predetermined region; and the performingthe 1/N of the first detection process uses substantially 1/N of theplurality of electrodes.
 4. The pointer position detection methodaccording to claim 1, wherein: the predetermined region includes aplurality of first electrodes and a plurality of second electrodes; theacquiring the partial detection data includes transmitting a pluralityof different predetermined signals to each of the plurality of firstelectrodes, and receiving a plurality of signals output from each of theplurality of second electrodes as a result of the transmitting; and theperforming the 1/N of the first detection process uses 1/N of each ofthe plurality of predetermined signals.
 5. The pointer positiondetection method according to claim 4, wherein: each of the plurality ofpredetermined signals includes N×M pulses; and the performing the 1/N ofthe first detection process includes using M pulses of the N×M pulses.6. The pointer position detection method according to claim 5, wherein:a number of the N×M pulses is equal to a number of the first electrodes.7. The pointer position detection method according to claim 5, wherein:the performing the 1/N of the first detection process includes deletingthe partial detection data retained in the memory and acquired N timesin case of a new acquisition of the partial detection data.
 8. Thepointer position detection method according to claim 1, wherein: theperforming the 1/N of the first detection process includes performingthe 1/N of the first detection process at predetermined intervals. 9.The pointer position detection method according to claim 8, furthercomprising: determining whether to perform the 1/N of the firstdetection process at the predetermined intervals, wherein: theperforming the 1/N of the first detection process and the combing areperformed when a result of the determining whether to perform the 1/N ofthe first detection process at the predetermined intervals is to performthe 1/N of the first detection process at the predetermined intervals.10. The pointer position detection method according to claim 8, furthercomprising: detecting a second pointer by performing a second detectionprocess at the predetermined intervals, wherein the second detectionprocess is different from the first detection process.
 11. The pointerposition detection method according to claim 10, wherein: the firstpointer is a first one of a passive pointer and an active pen; and thesecond pointer is a second one of the passive pointer and the activepen, the second one of the passive pointer and the active pen beingdifferent from the first one of the passive pointer and the active pen.